Glutamine's physiological and biochemical importance for epithelium of intestine and colon will be studied. Glutamine utilization by amidotransferases provides nitrogen to de novo synthetic pathways; and its hydrolysis by mitochondrial phosphate-dependent glutaminase forms ammonia and glutamate, a potential respiratory substrate. In vivo, glutamine is an important source of respiratory CO2 for rat intestine. Moreover, in different species of animals, there is a positive correlation between arterial glutamine concentration, the extent of net uptake of blood glutamine by gut, and mucosal glutaminase activity. We will study the metabolic fate and role of glutamine in vitro in tissue slices, everted sacs, and isolated epithelial cells, obtained from glutaminase-rich and glutaminase-deficient epithelium. The activity and location of several key enzymes, including glutamic-ketoacid transaminase, glutamine synthetase, glutamic dehydrogenase, glutaminase, malic enzyme, and phosphoenolpyruvate carboxykinase will be determined in order to more exactly delineate the sites of glutamine metabolism in the epithelium of small and large bowel. The ability of glutamine to promote transport, de novo purine and pyrimidine biosynthesis, and oxygen uptake (as compared with glucose and other potential respiratory substrates), and to preserve viability of intestinal tissue in vitro will be examined. Amino acid analogs, which can inhibit glutamine metabolism, will be employed to further clarify the relationship of metabolism to function.